Treating hydrocarbon fluids



April "i E943... H1. v. ATWELL TREATING HYDROGARBON FLUIDS Filed Deo. 29, 1958 ATTORNEY .INN

Patented Apr. 29, 194

UNITED STATES PATENT @ENCE TREATING HYDROCARBON FLUIDS HaroldV. Atwell, Beacon, N. Y., assigner to Process Management Company, Incorporated, New York, N. Y., a corporation of Delaware Application December 29, 1938, Serial No. 248,174

8 Claims.

This invention relates to the treatment of hydrocarbons.

According to my invention relatively heavy charging oil having a Wide boiling-range is preheated and is then fractionated to separate relatively heavy residual oil from a plurality of fractions including an intermediate hydrocarbon fraction containing heavy gasoline constituents, and a lighter hydrocarbon fraction containing light gasoline constituents. The intermediate hydrocarbon fraction maybe treated in any suitable manner to produce motor fuels, or it may be mixed with a portion of the lighter hydrocarbon fraction and treated to produce motor fuels. Gases and vapors remaining after fractionation are treated to separate normally gaseous hydrocarbons including C3 and C4 hydrocarbons and, if desired, C2 hydrocarbons from iixed gases such as hydrogen and methane. In some instances it may be desirable to mix allthe lighter hydrocarbon fraction with the normally gaseous hydrocarbons and pass this mixture through a conversion zone.

The relatively heavy residual oil and a portion of Vthe normally gaseous hydrocarbons including C3 and C4 constituents obtained from the charge oil and resulting from conversion treatment are introduced into a heating and conversion zone wherein they are maintained under superatmospheric pressure and at an elevated temperature to elfect the desiredextent of conversion during passage therethrough. The heating and cracking zone may take the form of a heating coil or a coil and drum may be used. The rest of the normally gaseous Vhydrocarbons is preferably introduced at successive points along the coil so as to give control over the proportion of normally gaseous hydrocarbons in the conversion zone. The distribution of the` normally gaseous hydrocarbons. will be controlled `by the extent of conversion at any given point in the heating coil.

During passage through the conversion zone, some of the higher boiling hydrocarbons will be converted into lower boiling hydrocarbons and some of the introduced gases may react with the lower boiling hydrocarbons formed during the conversion and undergo polymerization and .interaction to form higher boiling constituents. I am not to be restricted to this theory ofr the reactions occurring. However, some molecular rearrangement takes place which produces the results described by me. I believe that the presence of the gaseous hydrocarbons in the conver. sion zone tends to reduce rtar formation andfor this reason I am able to subject the relatively heavy oil to relatively high temperature and pressure conditions to obtain a high crack per pass.

A portion of the lighter hydrocarbon fraction containing light gasoline constituents such as C5 and Cs hydrocarbons is preferably recycled to the heating and conversion zone and is introduced into the latter portion of the heating and conversion zone after the introduction of the normally gaseous hydrocarbons. When higher boiling liquid hydrocarbons are converted into lower boiling hydrocarbons in the presence of normally gaseous hydrocarbons, large proportions of low boiling normally liquid hydrocarbons are formed. By recycling a portion of the lighter hydrocarbon fraction to the heating and conversion zone and mixing it with the heavy residual oil undergoing conversion in the presence of gaseous hydrocarbons, a larger proportion of higher boiling normally liquid hydrocarbons in the gasolineA range is formed during the conversion of the hydrocarbons passing through the heating and conversion Zone and in this Wayrthe tendency of obtaining excessive proportions of low boiling hydrocarbons is to some extent offset.

While my invention may be so carried on that insufficient amounts of `gas oil are formed for recycling, I have made provision for recycling of gas oil, if such recycling is desired. When it is desired to recycle and further crack gas oil, the gas oil is preferably introduced near the outlet end of the heating and conversion zone instead of being recycled to the inlet end of the heating and conversion zone. Y The products of conversion leaving the heating andvconversion zone are passed to an evaporator under lower pressure to separate liquid residue from vapors. 'I'he vapors are fractionated to separate gas oil from a heavy naphtha fraction containing heavy gasoline constituents, a light naphtha fraction containing C5 and C6 hydrocarbons ,normally included in gasoline and gases containing hydrogen, methane and C2, C3 and C4 hydrocarbons. The heavy naphtha fraction `may be further treated in any suitable man- `ner to obtain a motor fuel having the desired boiling range. A portion of the light naphtha fraction containing C5 and Ce hydrocarbons may be added to the heavy naphtha fraction to meet volatility requirements. Thegases are treatedv toseparate C3 and C4 and, if desired, C2 hydrocarbons therefrom `for recycling to the heating and conversionzone with similar gaseous hydrocarbons obtained from the` relatively heavy charging oil above described. A portion of the last mentioned light naphtha fraction containing the C5 and Cs hydrocarbons is preferably recycled to the heating and conversion zone with the fraction containing C5 and Ce hydrocarbons obtained from the relatively heavy charging oil above described.

Instead of fractionating a crude oil to obtain the reduced crude and the various fractions as above described I may use reduced crude oil and hydrocarbon fractions and hydrocarbon gasesv from extraneous sources.

In the drawing I have diagrammatically shown one form of apparatus adapted forpracticing my invention but it will be understood that I am not to be restricted thereto as other apparatus and other arrangements may be used to carry out the steps of my process. Y

Referring now to the drawing, the reference character Hl designates an inlet line for conveying the charge oil stock to the heating zone l2 in furnace or heater I4. The charging stock is one having a wide boiling range such as crude oil, reduced crude or gas oil. A pump I6 forces the charging oil through the heater coil l2 wherein Q the charging oil is maintained at a pressure from about atmospheric to about 250 pounds per square inch and is raised to a temperature of about 525 to 625 F. to vaporize relatively light constituents therein. The heated charging oil is passed through line I8 to a fractionating tower 29 which may be of bubble tower construction wherein the vapor-ized relatively light constituents are separated from the residual oil, such as a topped or reduced crude oil. The residual oil is withdrawn from the bottom of the fractionating tower 2G and passed through line 22 by pump 24 to a heating and conversion zone 28 in furnace 30 as will be later described in more detail.

The vaporized constituents remaining after fractionation in the fractionating tower 2U are passed through line 32 and introduced into the fractionating tower 34 wherein further fractionation is effected to separate an intermediate hydrocarbon fraction or heavy naphtha containing heavy gasoline constituents from lighter constituents. In some instances it may be desirable to separate kerosene or light gas oil in a conventional manner between the reduced crude and gasoline. The intermediate fraction is withdrawn from the bottom of the yfractionating tower 34 through line 36 and may be further fractionated to obtain a motor fuel having the desired boiling range. If desired, the intermediate hyn drocarbon fraction from fractionating tower 34 may be mixed with a lighter hydrocarbon fraction containing C5 and Cs hydrocarbons and passed through the latter portion of the conversion zone to raise the anti-knock value of the light hydrocarbon fraction. The vapors remaining after fractionation in the fractionating tower 34 are passed through line 38 toa fractionating tower 40 wherein further fractionation is effected to separate a lighter hydrocarbon fraction or light naphtha containing light normally liquid hydrocarbons, such as C5 and Cs hydrocarbons, and having a boiling range between about 100 and 150 F.

The light naphtha is withdrawn from the bottom of the fractionator 48 and passed through line 42 by pump 44. A portion of the liquid passing through line 42 may be passed through line 46 and admixed with the intermediate fraction withdrawn from the bottom of the fractionating tower 34 through line`36. Another portion or all compressed charge is then introduced into a fractionating tower 58 for separating liquefied normally gaseous hydrocarbons from the socalled iixed gases comprising hydrogen, and

methane together with ethane if desired, the

fixed gases being withdrawn through valved line The liquefied normally gaseous hydrocarbons are withdrawn from the bottom of the fractionating tower 58 and are passed through line 62 by pump 64, at least a portion of such normally gaseous hydrocarbons being admixed with the charge of residual oil passing through line 22 to the heating and conversion zone 28. This portion of the liquefied normally gaseous hydrocarbons is passed through line 68 and is then mixed with the reduced crude or residual oil before the residual oil is introduced into the heating and conversion zone 28.

Another portion of the liquefied normally gaseous hydrocarbons is preferably passed through line 10 into the heating and conversion zone 28 at the point 12 after the residual oil mixture containing the normally gaseous hydrocarbons Vfirst introduced has undergone some heating in the conversion zone 28. A third portion of the normally gaseous hydrocarbons may be'passed through line I4 into the heating and conversion zone 28 at the point 'I6 which is situated further along the heating and conversion zone 28. I prefer to introduce the recycled normally, gaseous hydrocarbons at successive points along the conversion zone so as to`control the proportion of the normally gaseous hydrocarbons in the conversion zone. More or less points4 of introduction of the normally gaseous hydrocarbons into the conversion Zone 28 may be used. The streams of normally gaseous hydrocarbons passing through lines 68, 10 and 14 are preferably preheated to approximately the temperature of the oil with which they are to be admixed in order to maintain high temperatures and rapid cracking rates in the conversion zone 28.

A portion of the light naphtha fraction containing C5 and'Cs hydrocarbons withdrawn from the bottom ofthe third fractionating tower 40 through line 50 is introduced into the heating and conversion zone 28 at the point 18 which is preferably located beyond the point of introduction of the normally gaseous hydrocarbons. I add this fraction containing C5 and Cs hydrocarbons in order to reduce the tendency to form excessive amounts of low boiling constituents during conversion. The light naphtha fraction passing through line 59 may be preheated to about the temperature of the oil with which it is to be admixed by being passed through a suit'- able preheater 19 to maintain the relatively high temperatures inthe conversion zone 28,

While my process is preferably carried out to obtain only small amounts of gas oil with corresponding high yields of gasoline, my process may also be carried out so as -to obtain sufficient amounts of gas oil for recycling and further conversion inl the heating and conversion zone 28.

`2,240,434. /W'here gas oil is to be recycled, it is passed through line 82 or line 84 or bothlines 82 and 84 into the latter portion of the heating and conversion zone 28 after the introduction of the liquefied normally gaseous hydrocarbons and ahead of or after the lighter liquid hydrocarbons containing C and C6 hydrocarbons as above described.

During the passage of the hydrocarbons through the heating and conversion zone 28, the hydrocarbons ar-e maintained under a pressure of about 500 to 1500 pounds per square inch and are raised to a temperatureof about 975 to 1050 F. to effect the desired conversion of the hydrocarbons. 'Ihe products of conversion leave the heating and conversion zone through line 86 and are passed through a heat exchanger 88 in order to reduce the temperature of the products of conversion. The partially cooled products of conversion are then passed through a pressure red-ucing valve 90 into an evaporator 62 under lower pressure for separating liquid residue from vapors. If desired, a quench oil may be introduced through line 94. The liquid residue is Withdrawn from the bottom of evaporator 92 through line 96. The vapors leave the top of the evaporator 02 and are passed through line |00 to a fractionating tower |02 for fractionating the vapors to separate insufficiently cracked oil as reflux condensate from vapors which pass overhead through line |04 and are introduced into a fractionating tower |06. The reflux condensate or condensate oil is withdrawn from the bottom of the fractionating tower |02 and passed through line |08 and may be withdrawn from the system through line |I0. If the process is carried out so as to obtain substantial quantities of condensate oil, it may be passed through line ||2 by pump ||4 and then through heat exchanger 88 for preheating the condensate oil. 'Ihe preheated condensate oil may be then further heated by being passed through heating coil ||8 in furnace or heater in order to preheat the condensate oil to about the temperature of the mixture passing through the heating and conversion Zone 28 at the point of admixture. The heated condensate oil is then passed through line |22 and through either line 82 or line 84 or both lines 82 and 84 into the latter portion of the heating and conversion Zone 28 as above described for further conversion into lower boiling hydrocarbons.

The vapors introduced into the fractionating tower |06 are further fractionated to separate a heavy naphtha fraction containing heavy gasoline constituents which is Withdrawn from the bottom of the fractionating tower |06 through line |26 and may be further treated as desired to obtain a motor fuel having a higher initial boiling point than usual, for example 150 F. The vapors remaining after fractionation in the fractionating tower |06 pass overhead through line |28 and are introduced into a fractionating tower |30 wherein further fractionation is effected to separate a light naphtha fraction having a boiling range of about 100 to 150 F. and containing C5 and Ce hydrocarbons. The light naphtha fraction is withdrawn from the bottom of the fractionator |30 and is passed through line |32 by pump |34. A portion of this liquid may be passed through line |36 for admixture with the heavy naphtha fraction passing through line |26. The rest of the light naphtha fraction may be passed through line |38 and admixed With the light naphtha fraction withdrawn from the bottom of the-fractionator 40 and then passed through line for further treatment in the heating and. conversion zone 28.

The vapors and gases remaining after fractionation in the fractionating tower |30 are passed through line |40 and preferably admixed with the gases leaving the fractionating tower 40 through line 52 and further treated to separate the so-called iixed gases from liquid normally gaseous hydrocarbons. If desired, the gases from the fractionating tower |30 may be separately treated to separate normally gaseous hydrocarbons therefrom.

Instead of removing the intermediate hydrocarbon fraction from fractionating tower 34 through line 36, it may be desirable in some instances to recycle this intermediate hydrocarbon fraction with the lighter liquid hydrocarbon fraction withdrawn from the bottom: of the fractionating tower 40 through line 42 and further treat this mixture in the heating and conversion zone 28, preferably introducing it into the conversion zone at about the point or points of introduction of the normally gaseous hydrocarbons to the conversion zone. It is also within the contemplation of my invention to recycle the liqueed normally gaseous products passing through line 62 to the conversion zone 28 with a portion of the low boiling normally liquid hydrocarbon fraction containing the C5 and C6 hydrocarbons to offset the tendency in the conversion zone 28 of forming a product having an excess of light hydrocarbon constituents.

In case the charge is deficient in light constituents this deficiency may be made up by supplying to line l0 gasoline and normally gaseous hydrocarbons from any convenient extraneous source.

While I have shown a plurality of fractionating towers in connection with the charge oil heater I2 and a plurality of fractionating towers in connection with the products of conversion from the heating and conversion Zone 28, it is to be understood that I may use a single fractionating tower in each instance and use trap out trays to separate the various fractions or to separate any desirable fractions.

While I have shown one form of apparatus and have given an example with specific operating conditions, it is to be expressly understood that I am not to be restricted thereto as other apparatus or other arrangements may be used and different operating conditions may be used with different charging stocks without departing from the spirit of my invention.

I claim:

1. A process for treating hydrocarbons to produce relatively low boiling hydrocarbons in the gasoline range which comprises heating a relatively heavy charging hydrocarbon oil to vaporize light constituents therein, separating vapors from residual oil, fractionating the vapors to separate relatively light hydrocarbons containing gasoline constituents from lighter normally liquid hydrocarbons and normally gaseous constituents, treating the normally gaseous constituents to separate C3 and C4 hydrocarbons therefrom, admixing the residual oil with at least a portion of the C3 and C4 hydrocarbons and introducing the mixture into a conversion zone wherein it is maintained under superatmospheric pressure and ai; an elevated temperature to eiect the desired extent of conversion, introducing another portion oi' the Ca and C4 hydrocarbons into the mixture undergoing conversion in said conversion zone, introducing at least a portion of the lighter normally liquid hydrocarbons into said conversion zone at a point subsequent to the addition of the C3 and C4 hydrocarbons, conducting the products of conversion away from said conversion zone and separating liquid residue from vapors, fractionating the separated vapors to separate condensate oil from lighter vapors, further fractionating the vapors to separatelight hydrocarbons containing gasoline constituents from a lighter liquid hydrocarbon fraction and normally gaseous constituents, admixing the normally gaseous constituents with the rst mentioned normally gaseous constituents for separation of C3 and C4 hydrocarbons, and returning at least a portion of the last mentioned lighter liquid hydrocarbon fraction to said conversion zone.

- 2. A process as dened in claim 1 wherein the condensate oil is introduced into the latter portion of the conversion zone subsequent to the introduction of the C3 and C4 hydrocarbons and the lighter liquid hydrocarbons for further treatment.

3. A process for treating hydrocarbons to produce relatively low boiling hydrocarbons in the gasoline range which comprises heating a relatively heavy charging hydrocarbon oil to vaporize light constituents therein, separating vapors `from residual oil, fractionating the vapors to separate relatively light hydrocarbons containing gasoline constituents from lighter normally liquid hydrocarbons and normally gaseous constituents, treating the normally gaseous constituents to separate C3 and C4 hydrocarbons therefrom, admixing the residual oil with at least a portion of the C3 and C4 hydrocarbons and introducing the mixture into a conversion zone wherein it is maintained under superatmospheric, pressure and at an elevated temperature to effect the desired extent of conversion, introducing a portion of the lighter normally liquid hydrocarbons into said conversion Zone at an intermediate point thereof, conducting the products of conversion away from said conversion zone and separating liquid residue from vapors, fractionating the separated vapors to separate condensate oil from light hydrocarbons containing gasoline constituents and normally gaseous constituents, separating C3 and C4. hydrocarbons from the last mentionad normally gaseous constituents, and returning the last mentioned Ca and Ci hydrocarbons to said conversion zone.

4. A process as defined in claim 3 wherein the condensate oil is introduced into the latter portion of the conversion zone subsequent to the introduction of the Cs and C4 hydrocarbons for further treatment.

5. A process for treating hydrocarbons to produce relatively low boiling hydrocarbons in the gasoline range which comprises heating a relatively heavy charging hydrocarbon oil to vaporize light constituents therein, separating vapors from residual oil, fractionating the vapors to separate relatively light hydrocarbons containing gasoline constituents from lighter normally liquid hydrocarbons and normally gaseous constituents, treating the normally gaseous constituents to separate C3 and C4 hydrocarbons therefrom, admixing the residual oil With at least a portion of the C3 and C4 hydrocarbons and introducing the mixture into a conversion zone wherein it is maintained under superatmospheric pressure and at an elevated temperature to effect the desired extent of conversion, introducing additional quantities of the C3 and C4 hydrocarbons into the mixture undergoing conversion at successive points along said conversion zone, introducing at least a portion of the lighter normally liquid hydrocarbons into said conversion zone at a point subsequent to the addition of the C3 and C4 hydrocarbons, conducting the products of conversion away from said conversion Zone and separating liquid residue from vapors, fractionating the separated vapors 1 to separate condensate oil from lighter vapors, further fractionating the lighter vapors to separate light hydrocarbons containing gasoline constituents from a lighter liquid hydrocarbonv fraction, and returning a portion of the last mentioned lighter liquid hydrocarbon fraction to said conversion zone.

6. A process for treating hydrocarbons to produce relatively low boiling hydrocarbons in the gasoline range which comprises heating a relatively heavy charging hydrocarbon oil to vaporize light constituents, separating vapors from residual oil, fractionating the vapors to separate a heavy naphtha fraction containing heavy gasoline constituents from a light naphtha fraction containing light gasoline constituents and normally gaseous constituents, treating the normally gaseous constituents to separate C3 and C4 hydrocarbons therefrom, admixing the residual oil with at least a portion of the C3 and C4 hydrocarbons and introducing the mixture into a conversion zone wherein it is maintained under superatmospheric pressure and at an' elevated temperature to eifect the desired extent of conversion, introducing additional quantities of the C3 and C4 hydrocarbons into the mixture undergoing conversion at successive points along said [conversion zone, introducing a portion of the light naphtha fraction into said conversion zone at a point subsequent to the addition of the C3 and Ct, hydrocarbons, conducting the products of conversion away from said conversion zone and separating liquid residue from vapors, fractionating the separated vapors to separate condensate oil from. lighter vapors, further fractionating the lighter vapors to separate a heavy naphtha fraction containing heavy gasoline constituents from a light naphtha fraction con-l taining light gasoline -constituents and introducing at least a portion of the last mentioned light naphtha fraction into the mixture passing through said ,conversion zone at a po-int subsequent to the introduction of the C3 and C4 hydrocarbons.

7. A process for treating hydrocarbons to produce motor fuels'which comprises mixing a relatively heavy hydrocarbon oil with normally gaseous hydrocarbons and passing such mixture through a conversion zone wherein it is maintained under superatmospheric pressure and at an elevated temperature, introducing additional quantities of normally gaseous hydrocarbons into the hydrocarbon mixture undergoing conversion at successive points along said conversion zone, introducing relatively light normally liquid hydrocarbons into said conversion zone at a point subsequent to the 'introduction of the normally gaseous hydrocarbons and admixingY them with the hydrocarbon mixture undergoing conversion, conducting the products of conversion away from said conversion Zone and separating liquid residue from vapors, fractionating the vapors to separate condensate oil from a relatively light hydrocarbon fraction [containing gasoline constituents and a lighter hydrocarbon fraction containing normally liquid hydrocarbons, and introducing at least a portion of the lighter hydrocarbon fraction into said conversion zone at a point subsequent to the introduction of all of the normally gaseous hydrocarbons.`

8. A process for treating hydrocarbons to produce motor fuels which comprises mixing a relatively heavy hydrocarbon oil Withfv normally gaseous hydrocarbons and passing such mixture through a conversion `zone wherein it is maintained under superatmospheric pressure and 1' at an elevated temperature, introducing relatively light normally liquid hydrocarbons into said conversion zone and admixing them with the hydrocarbon mixture undergoing conversion, lconducting the products of conversion away from said conversion zone and separating liquid residue from vapors, fraction-ating the vapors to separate condensate oil from a relatively light hydrocarbon fraction containing gasoline constituents and a lighter hydrocarbon fraction containing normally liquid hydrocanbons, and recycling at least a portion of the lighter hydrocarbon fraction to said conversion zone.

HAROLD V. ATWELL. 

